Polishing pad for substrate polishing apparatus and substrate polishing apparatus having polishing pad

ABSTRACT

A polishing pad of a typical substrate polishing apparatus is a consumable item. In the substrate polishing apparatus of the prior art, it is determined that the service life of the polishing pad has expired when the polishing pad is used by a predetermined number of times or for a predetermined period of time. In a case where the serviceable life of the polishing pad still remains in practice even when the service life has expired, the still usable polishing pad is to be replaced. Disclosed is a substrate polishing apparatus including a polishing table for installing a polishing pad having a transparent window and an indicator provided in the polishing table to check deterioration of the transparent window and provided in a location visually observable through the transparent window.

CROSS-REFERENCE TO RELATED APPLICATION

This application is based upon and claims the benefit of priority of the prior Japanese Patent Application No. 2018-122076, filed on Jun. 27, 2018, the entire contents of which are incorporated herein by reference.

TECHNICAL FIELD

The present invention relates to a polishing pad for a substrate polishing apparatus and a substrate polishing apparatus having the polishing pad.

BACKGROUND ART

In the prior art, there is known an apparatus of polishing a substrate using a polishing pad installed in a polishing table. For example, PTL 1 (Japanese Unexamined Patent Application Publication No. 2003-197587) discusses a substrate polishing apparatus including a rotatable platen and a polishing pad (“grinding material” of PTL1) installed on the platen (FIG. 1).

CITATION LIST Patent Literature

PTL1: Japanese Unexamined Patent Application Publication No. 2003-197587

SUMMARY OF INVENTION Technical Problem

In a general substrate polishing apparatus, a polishing pad is a consumable item. In the substrate polishing apparatus of the prior art, the maximum number of use or the maximum service life of the polishing pad is set on0 the basis of a wear amount or the like measured or calculated in advance. That is, in the substrate polishing apparatus of the prior art, it is determined that the service life of the polishing pad has expired when the polishing pad is used for a predetermined number of times or for a predetermined period of time (hereinafter, simply referred to as “a predetermined number of times”). However, it is difficult to say that the serviceable life of the polishing pad has expired at the very moment that the polishing pad is used for a predetermined number of times. In a case where the service life of the polishing pad has expired before it is used for a predetermined number of times, the substrate is polished by the polishing pad whose service life has expired. Therefore, the substrate polishing apparatus may not exhibit a predetermined polishing performance. Meanwhile, in a case where the service life of the polishing pad does not expire even when it is used for a predetermined number of times, the still usable polishing pad is replaced. By replacing the still usable polishing pad, the replacement cycle of the polishing pad is shortened, and the replacement cost increases.

In this regard, it is therefore an object of this application to address at least a part of the aforementioned problems.

Solution to Problem

This application discloses a substrate polishing apparatus as one embodiment. The substrate polishing apparatus includes: a polishing table for installing a polishing pad having a transparent window; and an indicator provided in the polishing table to check deterioration of the transparent window in a location visually observable through the transparent window.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a front cross-sectional view illustrating a substrate polishing apparatus;

FIG. 2 is a top view illustrating polishing table installed with a polishing pad;

FIG. 3 is a top view illustrating the polishing table;

FIG. 4 is an enlarged view illustrating an alignment mark;

FIGS. 5A and 5B are top views illustrating a part of the polishing table installed with the polishing pad, in which FIG. 5A is a diagram illustrating a case where the polishing pad 150 is not appropriately aligned, and FIG. 5B is a diagram illustrating a case where the polishing pad 150 is appropriately aligned;

FIG. 6 is a top view illustrating a polishing table having an indicator;

FIGS. 7A and 7B are diagrams illustrating the indicator positioned in the left half of FIG. 6 as observed through a transparent window, in which FIG. 7A is a diagram illustrating a case where the transparent window is not deteriorated, and FIG. 7B is a diagram illustrating a case where the transparent window is deteriorated;

FIGS. 8A and 8B are diagrams illustrating the indicator positioned in the right half of FIG. 6 as observed through the transparent window, in which FIG. 8A is a diagram illustrating a case where the transparent window is not deteriorated, and FIG. 8B is a diagram illustrating a case where the transparent window is deteriorated;

FIG. 9 is a front cross-sectional view illustrating a substrate polishing apparatus having an image sensing mechanism; and

FIG. 10 is a front cross-sectional view illustrating a substrate polishing apparatus having a light source.

DESCRIPTION OF EMBODIMENTS First Embodiment Background and Objects of First Embodiment

The substrate polishing apparatus of PTL 1 (Japanese Unexamined Patent Application Publication No. 2003-197587) is configured such that a polishing progress can be measured using a liquid seal type sensor provided under a polishing table (also referred to as “platen”). In order to allow the irradiation light irradiated from the sensor and the sealing liquid to pass through the inside of the platen, the platen of PTL1 has a liquid supply port. Similar to the liquid supply port, the polishing pad of PTL1 has a through-hole.

In the apparatus of PTL1, a flow of the sealing liquid in the vicinity of the substrate may be disturbed when the liquid supply port and the through-hole are misaligned. If the flow of the sealing liquid is disturbed, it is considered that performance of the sensor unit may be degraded. Therefore, in the technique of PTL1, it is desirable that the polishing pad is accurately aligned with the platen.

In general, the polishing pad is formed of a non-transparent material. When the non-transparent polishing pad is installed in the platen, most of the platen is covered by the polishing pad except for the portion exposed through the through-hole. Therefore, it is difficult to align the polishing pad while visually observing the position of the liquid supply port. In addition, in recent years, the size of the substrate is increasing. As the size of the substrate increases, the platen and the polishing pad also tend to increase in size. It is difficult to install a large-sized polishing pad in a large-sized platen and align the large-sized polishing pad. Furthermore, the technique of PTL1 is obtained by assuming that only a single sensor unit is provided. However, the polishing apparatus has a plurality of sensor units in some cases. If a plurality of sensor units are provided, much effort is necessary to align the polishing pad. Therefore, it is demanded to facilitate alignment of the polishing pad.

<Summary of Substrate Polishing Apparatus 100>

FIG. 1 is a front cross-sectional view illustrating a substrate polishing apparatus 100 according to a first embodiment of this disclosure. FIG. 2 is a top view illustrating a polishing table 110 installed with a polishing pad 150. However, the drawings used herein are just schematic. Dimensions, shapes, positions, or the like of the elements illustrated in each drawing do not necessarily match those of the actual devices. The letters “PAD” and “TABLE” shown in some of the drawings are letters for distinguishing the upper surface of the polishing pad 150 and the upper surface of the polishing table 110. That is, the letters “PAD” and “TABLE” in the drawings do not refer to elements of the substrate polishing apparatus 100. In addition, in the drawings attached herein, there may be a difference between the configuration shown in the top view and the configuration shown in the cross-sectional view in some cases. For example, in FIG. 2, the sealing liquid supply path 111 and the sealing liquid discharge path 112 are arranged in the circumferential direction of the polishing table 110 (in the circumferential direction of the polishing pad 150). However, in FIG. 1, the sealing liquid supply path 111 and the sealing liquid discharge path 112 are arranged in the radial direction of the polishing table 110. This difference is just caused by convenience of illustration. In order to embodying the concept disclosed herein, the sealing liquid supply path 111 and the sealing liquid discharge path 112 may be arranged either in the circumferential direction or in the radial direction of the polishing table 110. Note that a positional relationship between the sealing liquid supply path 111 and the sealing liquid discharge path 112 is not limited to the illustrated positional relationship.

The substrate polishing apparatus 100 according to this embodiment is a chemical mechanical polishing (CMP) apparatus. The substrate polishing apparatus 100 may be any apparatus other than the CMP apparatus as long as the polishing progress is measured using a detector from the lower surface of the polishing table. The substrate polishing apparatus 100 includes a polishing table 110, a liquid seal type optical sensor 120, a polishing head 130, and a polish liquid supply mechanism 140. A polishing pad 150 is detachably installed on the upper surface of the polishing table 110. A substrate 131 is detachably installed on the lower surface of the polishing head 130.

<Polishing Table 110>

The polishing table 110 is configured to be rotatable in at least one direction by a motor (not shown) or the like. Depending on the type of the substrate polishing apparatus 100, the polishing table 110 may not be rotatable. The polishing table 110 is provided with a sealing liquid supply path 111 and a sealing liquid discharge path 112. The sealing liquid supply path 111 is provided to supply a sealing liquid to the through-hole 151 of the polishing pad 150 disposed on the upper surface of the polishing table 110 (the through-hole 151 will be described below). The sealing liquid discharge path 112 is provided to discharge the sealing liquid from the through-hole 151.

The sealing liquid supply path 111 is connected to a sealing liquid source 113. There is no limitation in the number of the sealing liquid sources 113. The sealing liquid source 113 may also be an element of the substrate polishing apparatus 100. A sealing liquid source 113 independent from the substrate polishing apparatus 100 may also be employed. The sealing liquid is, for example, pure water. However, any other liquid may also be employed as the sealing liquid. The sensing light of the optical sensor 120 travels through the sealing liquid. Therefore, it is preferable that the sealing liquid is substantially transparent at least within the sensing light wavelength range. Note that the “sensing light” refers to “irradiation light traveling from the optical sensor 120 to the substrate 131” and “reflection light traveling from the substrate 131 to the optical sensor 120”.

After the sealing liquid is supplied to the optical path of the sensing light, it is discharged to the outside of the polishing table 110 via the sealing liquid discharge path 112. The sealing liquid discharged to the outside of the polishing table 110 may return to the sealing liquid source 113 as illustrated in FIG. 1. The sealing liquid may be discarded without returning to the sealing liquid source 113. The sealing liquid supply path 111, the sealing liquid discharge path 112, and the sealing liquid source 113 may be connected to each other with a rotary joint 114.

As described below, two optical sensors 120 are provided in this embodiment. Therefore, the sealing liquid supply path 111 of FIG. 1 is configured to branch into two paths so that the sealing liquid is supplied to each of the optical sensors 120. Similarly, the sealing liquid discharge path 112 of FIG. 1 is configured to join the two paths. However, a configuration other than that illustrated in the drawing may also be employed. For example, for each of the two optical sensors 120, two independent sealing liquid supply paths 111 and two independent sealing liquid discharge paths 112 may be provided.

<Optical Sensor 120>

The optical sensor 120 is a sensor for measuring a polishing progress of the substrate 131. Specifically, the optical sensor 120 irradiates light onto a polished surface of the substrate 131 and measures an optical property of reflection light. Since the optical property of the reflection light may change depending on a state of the polished surface of the substrate 131, it is possible to measure the polishing progress by measuring the optical property of the reflection light. The optical sensor 120 may be a sensor for measuring a polishing amount of the substrate 131. The optical sensor 120 may be a sensor for detecting a polishing endpoint of the substrate 131.

The substrate polishing apparatus 100 according to this embodiment has two optical sensors 120. More specifically, one of the optical sensors 120 is provided in the vicinity of the center of the polishing table 110, and the other optical sensor 120 is provided in the vicinity of the edge of the polishing table 110. Which region of the substrate 131 is measured is determined on the basis of a distance between the optical sensor 120 and a rotational axis of the polishing table 110. In other words, the measurement region of the substrate 131 depends on the distance between the optical sensor 120 and the rotational axis of the polishing table 110. The number and arrangement of the optical sensors 120 are just exemplary, and any other configuration may also be employed. For example, a plurality of optical sensors 120 may be provided concentrically so as to increase measurement frequency of the substrate 131 in a specific region.

The optical sensor 120 has a sensor body 121, an irradiation light optical fiber 122, and a reflection light optical fiber 123. For convenient illustration purposes, in FIG. 2, the irradiation light optical fiber 122 and the reflection light optical fiber 123 are painted black. According to this embodiment, a sensor body 121 is provided in the lower part of the polishing table 110. The sensor body 121 includes a light source (not shown) for irradiating light to the irradiation light optical fiber 122 and a photodetector (not shown) for measuring reflection light passing through the reflection light optical fiber 123.

The irradiation light optical fiber 122 and the reflection light optical fiber 123 extend from the sensor body 121. The irradiation light optical fiber 122 and the reflection light optical fiber 123 extend from the lower part of the polishing table 110 to the upside of the polishing table 110 and reach the inside of the sealing liquid supply path 111. The sealing liquid supply path 111 may also be referred to as an opening for passing the optical fiber extending from the sensor body 121 (including the irradiation light optical fiber 122 and the reflection light optical fiber 123). As long as the irradiation light optical fiber 122 and the reflection light optical fiber 123 do not protrude from the upper surface of the polishing pad 150, and the measurement using the optical sensor 120 is possible, the upper ends of the irradiation light optical fiber 122 and the reflection light optical fiber 123 may be placed in any position. Typically, the upper ends of the irradiation light optical fiber 122 and the reflection light optical fiber 123 may be placed slightly under the upper surface of the polishing table 110.

A wiring line (not shown) may be provided to supply power to the sensor body 121 and transmit a signal from the sensor body 121. The wiring line may be connected to the sensor body 121 with a rotary joint (including the rotary joint 114 or other types of rotary joints). The signal from the sensor body 121 may be received by a controller (not shown). The wiring line may be omitted by employing a wireless transmission technology or the like. The controller that receives, from the sensor body 121, a signal indicating that “the substrate 131 has been polished by a predetermined amount” or “the polishing of the substrate 131 has reached the endpoint” may stop the polishing of the substrate 131 by controlling the substrate polishing apparatus 100 so as to execute at least one of steps (1) to (4) as follows: (1) lifting the polishing head 130; (2) stopping rotation of the polishing head 130; (3) stopping rotation of the polishing table 110; and (4) stopping supply of the polish liquid from the polish liquid supply mechanism 140.

<Polishing Head 130>

The polishing head 130 is provided over the polishing table 110 to face the polishing table 110. The substrate 131 is detachably installed on the lower surface of the polishing head 130. The polishing head 130 is configured to rotate by a motor (not shown) at least in one direction and preferably in the same direction as that of the polishing table 110. The polishing head 130 is configured to be vertically moveable by a vertical movement mechanism (not shown) or the like. As the polishing head 130 is lowered by the vertical movement mechanism, the substrate 131 is pressed to the polishing pad 150. As at least one or preferably both of the polishing head 130 and the polishing table 110 rotate while the substrate 131 is pressed to the polishing pad 150, the substrate 131 is polished.

<Polish Liquid Supply Mechanism 140>

The polish liquid supply mechanism 140 is provided over the polishing table 110. A tip of the polish liquid supply mechanism 140 has a nozzle shape, so that the polish liquid (slurry) or the like can be supplied to the polishing pad 150. Without limiting to the polish liquid, the polish liquid supply mechanism 140 may supply a cleaning liquid and/or a chemical solution. Unlike the configuration of this embodiment, a configuration of supplying the polish liquid from the lower surface of the polishing table 110, a configuration of supplying the polish liquid from the inside of the polishing head 130, or the like may also be employed.

<Polishing Pad 150>

The polishing pad 150 is a plate-like member installed on the upper surface of the polishing table 110. Note that the polishing pad 150 may also be referred to as a “cloth-like member” depending on a material, a thickness, or the like of the polishing pad 150 in some cases. In general, the polishing pad 150 is formed of a non-transparent material (such as polyurethane foam).

It is necessary to provide the through-hole 151 in the polishing pad 150 in order to pass the sensing light and the sealing liquid. In a case where an opening is provided in the polishing pad 150, it is necessary to position the polishing pad 150 such that the opening is located in the upper part of the sealing liquid supply path 111 or the like. However, since the polishing pad 150 is generally non-transparent, it is difficult to align the polishing pad 150 while visually observing the positions of the sealing liquid supply path 111 and the sealing liquid discharge path 112. Note that “aligning the polishing pad 150” may also be read as “adjusting an installation position and/or angle of the polishing pad 150”.

In this regard, the polishing pad 150 according to this embodiment is provided with a transparent window 152. Preferably, the transparent window 152 is substantially transparent at least within a visible light wavelength range. The transparent window 152 may be formed of, for example, polycarbonate resin, acrylic resin, polyvinyl chloride resin, polystyrene resin, polyurethane resin, polyester resin, or the like. A through-hole 151 is provided in the center of the transparent window 152. This may also be expressed as “an annular transparent window 152 is provided around the through-hole 151”. However, the terminology “annular” here also refers to an angled ring shape as well as a circular ring shape. As illustrated in FIG. 2, the through-hole 151 has an elliptical shape. However, the through-hole 151 may have a circular shape or an angled shape. In a case where the polishing pad 150 is appropriately installed in the polishing table 110, the through-hole 151 communicates with the sealing liquid supply path 111 and the sealing liquid discharge path 112. As described above, the substrate polishing apparatus 100 according to this embodiment has two optical sensors 120. According to this embodiment, two sets of the sealing liquid supply path 111 and the sealing liquid discharge path 112 are provided to match the number of the optical sensors 120. In addition, two through-holes 151 are provided in the polishing pad 150 according to this embodiment to match the numbers of the sealing liquid supply paths 111 and the sealing liquid discharge paths 112. More specifically, one of the through-holes 151 is provided in the vicinity of the center of the polishing pad 150, and the other through-hole 151 is provided in the vicinity of the edge of the polishing pad 150. Which region of the substrate 131 is measured is determined on the basis of a distance between the through-hole 151 and the center of the polishing pad 150. In other words, the measurement region of the substrate 131 depends on the distance between the through-hole 151 and the center of the polishing pad 150.

In a case where the polishing pad 150 according to this embodiment is installed in the polishing table 110, it is possible to visually observe a portion of the polishing table 110 placed in the lower part of the transparent window 152 as well as a portion of the polishing table 110 exposed through the through-hole 151. Therefore, in a case where the polishing pad 150 according to this embodiment is installed in the polishing table 110, it is possible to easily align the polishing pad 150 while visually observing the locations of the sealing liquid supply path 111 and the sealing liquid discharge path 112.

Note that the configuration of the substrate polishing apparatus 100 is merely exemplary. In particular, any configurations known in the art (for example, the configuration disclosed in PTL1) may be employed as the configurations of the polishing table 110 and the optical sensor 120. For example, a plurality of irradiation light optical fibers 122 and reflection light optical fibers 123 may be connected to a single sensor body 121.

Second Embodiment Summary of Second Embodiment

In the second embodiment, a substrate polishing apparatus 100 having an alignment mark 300 on the polishing table 110 in order to further facilitate alignment of the polishing pad 150 will be described. FIG. 3 is a top view illustrating the polishing table 110 according to this embodiment. FIG. 4 is an enlarged view illustrating the alignment mark 300. FIGS. 5A and 5B are top views illustrating a part of the polishing table 110 installed with the polishing pad 150 to show a state of the alignment of the polishing pad 150 using the alignment mark 300. FIG. 5A is a diagram illustrating a case where the polishing pad 150 is not appropriately aligned. FIG. 5B is a diagram illustrating a case where the polishing pad 150 is appropriately aligned.

<Alignment Mark 300>

The alignment mark 300 is a mark provided on the upper surface of the polishing table 110. Specifically, the alignment mark 300 is provided in the vicinities of the sealing liquid supply path 111 and the sealing liquid discharge path 112. More specifically, at least a part of the alignment mark 300 is configured to be placed directly under the transparent window 152 when the polishing pad 150 is appropriately installed in the polishing table 110. The alignment mark 300 is used to align the polishing pad 150 with the polishing table 110. The alignment mark 300 is configured to be visually recognizable by a user of the substrate polishing apparatus 100. However, in a case where the alignment mark 300 is observed using any image sensing device or the like instead of a user, the alignment mark 300 may be visible to the image sensing device or the like although it is invisible to the user. The alignment mark 300 may be formed by any method such as laser marking, painting, printing, or scribing. In order to illustrate the alignment mark 300 distinguishably from the through-hole 151 and the like, the alignment mark 300 is indicated by a dotted line in FIGS. 3, 4, 5A, and 5B. However, the alignment mark 300 may not have a dotted line shape in an actual apparatus.

Preferably, the alignment mark 300 has a first mark 310 corresponding to an outer edge of the transparent window 152. Specifically, the first mark 310 matches the outer edge of the transparent window 152 when the polishing pad 150 is appropriately installed in the polishing table 110. Preferably, the alignment mark 300 further has a second mark 320 corresponding to the outer edge of the through-hole 151. Specifically, the second mark 320 matches the outer edge of the through-hole 151 when the polishing pad 150 is appropriately installed in the polishing table 110. For example, the first mark 310 has a circular shape, and the second mark 320 has an elliptical shape. More preferably, the alignment mark 300 includes a third mark 330 having a cross shape. If the through-hole 151 has an elliptical shape, the cross-shaped third mark 330 is preferably configured to match major and minor axes of the through-hole 151. Specifically, the cross-shaped third mark 330 matches the major and minor axes of the through-hole 151 when the polishing pad 150 is appropriately installed in the polishing table 110. Note that, in FIG. 4, a part of the third mark 330 is disconnected. In the part where the third mark 330 is disconnected, the sealing liquid supply path 111 and the sealing liquid discharge path 112 are placed. The alignment mark 300 may include a fourth mark 340, for example, having a circular shape between the first and second marks 310 and 320.

As illustrated in FIG. 5A, in a case where the polishing pad 150 is not appropriately aligned, the first and second marks 310 and 320 can be visually observed through the transparent window 152 or the through-hole 151. A positional deviation amount of the polishing pad 150 can be perceived by comparing the outer edge of the transparent window 152 and the first mark 310. The positional deviation amount of the polishing pad 150 can also be perceived by comparing the outer edge of the through-hole 151 and the second mark 320. In addition, a rotation amount of the polishing pad 150 can also be perceived on the basis of an inclination state of the second mark 320 and/or the third mark 330. The polishing pad 150 can be appropriately aligned by adjusting an installation position and/or angle of the polishing pad 150 on the basis of the perceived positional deviation amount and/or rotation amount.

As illustrated in FIG. 5B, in a case where the polishing pad 150 is appropriately aligned, the outer edge of the transparent window 152 and the first mark 310 overlap on each other, so that the first mark 310 becomes nearly invisible. Similarly, in a case where the polishing pad 150 is appropriately aligned, the outer edge of the through-hole 151 and the second mark 320 overlap on each other, so that the second mark 320 becomes nearly invisible.

By providing the alignment mark 300, it is possible to easily align the polishing pad 150 against the polishing table 110 with high accuracy. Note that the shape of the alignment mark 300 is merely exemplary. In the simplest case, the alignment mark 300 may be a simple spot. In addition, any mark that can be used for alignment may be employed. In a case where any image sensing device observes the alignment mark 300, the positional deviation amount and/or the rotation amount or the like of the polishing pad 150 may be calculated by a controller of a computer or the like.

Third Embodiment Summary of Third Embodiment

In a general substrate polishing apparatus, the polishing pad is a consumable item. In the substrate polishing apparatus of the prior art, the maximum number of use or the maximum service life of the polishing pad has been set on the basis of the wear amount or the like measured or calculated in advance. That is, in the substrate polishing apparatus of the prior art, it is determined that the service life of polishing pad has expired if the polishing pad is used for a predetermined number of times or for a predetermined period of time (hereinafter, simply referred to as “predetermined number of times”). However, it is difficult to say that the serviceable life of the polishing pad has expired at the very moment that the polishing pad is used for a predetermined number of times. In a case where the service life of the polishing pad has expired before a predetermined number of times, the substrate is polished by the polishing pad whose service life has expired. Therefore, the substrate polishing apparatus may not exhibit predetermined polishing performance. Meanwhile, in a case where the service life of the polishing pad has not expired even when it is used for a predetermined number of times, the polishing pad which is still usable is replaced. If the still usable polishing pad is replaced, the replacement cycle of the polishing pad is shortened, and the replacement cost increases.

In order to address the aforementioned problems, according to the third embodiment, a substrate polishing apparatus 100 having an indicator on the polishing table 110 will be described. FIG. 6 is a top view illustrating the polishing table 110 having the indicator 600.

<Indicator 600>

At least a part of the indicators 600 are provided in a region of the polishing table 110 directly under the transparent window 152 of the polishing pad 150 when the polishing pad 150 is appropriately installed. In other words, the indicator 600 is provided in a location visually recognizable through the transparent window 152 when the polishing pad 150 is appropriately installed in the polishing table 110. Furthermore, in other words, the indicator 600 is provided on a surface of the polishing table 110 where the polishing pad 150 is installed, and the indicator 600 is provided around an opening (including the sealing liquid supply path 111 or the opening 610 which will be described in details below) for passing the optical fibers (including the irradiation light optical fiber 122 and the reflection light optical fiber 123). Note that, unlike the embodiments described above, the optical sensor 120 may be a liquid seal type or not. In the example of FIG. 6, the sealing liquid supply path 111 and the reflection light optical fiber 123 placed in the right half of the drawing are connected to the liquid seal type optical sensor 120. Since the liquid seal type optical sensor 120 has been described in the aforementioned embodiment, it will not be described repeatedly. Meanwhile, in the example of FIG. 6, the irradiation light optical fiber 122 and the reflection light optical fiber 123 located in the left half of the drawing are connected to the non-liquid seal type optical sensor 120. Therefore, the sealing liquid supply path 111 and the sealing liquid discharge path 112 are not provided in the polishing table 110 in the left half of the drawing. As a substitute for the sealing liquid supply path 111 and the sealing liquid discharge path 112, an opening 610 for passing the optical fiber and transmitting the sensing light is provided in the polishing table 110 as illustrated in the left half of the drawing. However, the configurations of the optical sensor 120 and its accessory elements are exemplary, and a configuration other than that illustrated in FIG. 6 may also be employed.

In FIG. 6, a set of indicators 600 includes four patterns (including a narrow stripe pattern, a wide stripe pattern, a narrow grid pattern, and a wide grid pattern). However, as long as deterioration of the transparent window 152 can be recognized as described below, a specific configuration of the indicator 600 is not limited to that illustrated in FIG. 6. For example, the indicator 600 may have an arbitrary number of patterns. In the simplest case, the indicator 600 may be a simple spot. The indicator 600 is configured to be visible by a user of the substrate polishing apparatus 100. However, in a case where the indicator 600 is photographed by any image sensing mechanism (for example, the image sensing mechanism 900 of FIG. 9) or the like instead of a user, the indicator 600 may not be visible for the user as long as it is recognizable by the image sensing mechanism or the like. The indicator 600 may be formed using any method such as laser marking, painting, printing, or scribing.

In a case where a new polishing pad 150 is used, the transparent window 152 is also a new item. Therefore, the optical properties of the transparent window 152 such as a transmittance, a refractive index, a reflectance, and a scattering degree do not change. However, as the substrate polishing apparatus 100 is driven, the substrate 131 is polished, and the transparent window 152 is worn. The wear of the transparent window 152 is particularly significant during dressing of the polishing pad 150. It is considered that the optical property of the transparent window 152 changes as the transparent window 152 wears. In the following description, a change of the optical property of the transparent window caused by wear will be referred to as “deterioration of the transparent window”. It is considered that how and what type of the optical property changes by the deterioration depends on a specific process, the type of the employed polishing liquid, a material of the substrate 131, a material of the transparent window 152, a material of the dresser, and the like. Here, it is assumed that the transmittance of the transparent window 152 is reduced. FIGS. 7A and 7B are diagrams illustrating a state of the indicator 600 placed in the left half of FIG. 6 as observed through the transparent window 152 of the polishing pad 150. FIG. 7A is a diagram illustrating a case where the transparent window 152 is not deteriorated. FIG. 7B is a diagram illustrating a case where the transparent window 152 is deteriorated. FIGS. 8A and 8B are diagrams illustrating a state of the indicator 600 placed in the right half of FIG. 6 as observed through the transparent window 152 of the polishing pad 150. FIG. 8A is a diagram illustrating a case where the transparent window 152 is not deteriorated. FIG. 8B is a diagram illustrating a case where the transparent window 152 is deteriorated. In FIGS. 7A, 7B, 8A, and 8B, the transmittance of the transparent window 152 is indicated by the hatching thickness in the transparent window 152. Specifically, as the hatching thickness increases, the transmittance of the transparent window 152 decreases.

As the transparent window 152 is deteriorated, appearance of the indicator 600 as observed through the transparent window 152 also changes. For example, since the transmittance of the transparent window 152 is reduced in FIGS. 7B and 8B, the indicator 600 is difficult to see. It is possible to perceive deterioration of the transparent window 152 from a change of appearance of the indicator 600. Since the deterioration of the transparent window 152 occurs simultaneously with the wear of the polishing pad 150, it is possible to indirectly perceive the wear amount of the polishing pad 150 by perceiving the deterioration of the transparent window 152. By perceiving the wear amount of the polishing pad 150, it is possible to replace the polishing pad 150 at a suitable timing.

The replacement timing of the polishing pad 150 may be determined, for example, on the basis of at least one of the following parameters: (1) brightness of the indicator 600; (2) sharpness of the edge portion of the indicator 600; (3) a contrast ratio between a predetermined spot of the indicator 600 and any other spot (regardless of the inside or outside of the indicator 600); and (4) a color tone of the indicator 600 when the indicator 600 is observed through the transparent window 152. In a case where the indicator 600 has a pattern in which a predetermined shape is repeated (such as a stripe pattern or a grid pattern), the replacement timing of the polishing pad 150 may be determined on the basis of (5) whether or not any pattern is distinguishable from its neighboring patterns, that is, whether or not the pattern of the indicator 600 is distinguishable when the indicator 600 is observed through the transparent window 152. Note that the aforementioned parameters (1) to (5) are merely exemplary. A threshold value may be appropriately set in the determination based on the aforementioned parameters (1) to (5). For example, a user may replace the polishing pad 150 at an arbitrary timing between a time point at which one type of the pattern (for example, narrow grid pattern) of the indicators 600 is not distinguishable and a time point at which all types of the pattern of the indicators 600 are not distinguishable. The replacement timing of the polishing pad 150 may be determined as a user visually observes the indicator 600. Meanwhile, in a case where the substrate polishing apparatus 100 includes any image sensing mechanism (for example, an image sensing mechanism 900 in FIG. 9 as described below), the indicator 600 may be observed by the image sensing mechanism. In a case where the indicator 600 is observed using the image sensing mechanism, the replacement timing of the polishing pad 150 may be determined on the basis of any image processing technique known in the art.

In the configured described hereinbefore, the polishing pad 150 can be replaced at a suitable timing. In addition, once the indicator 600 is visually observed, it is possible to perceive the wear amount of the polishing pad 150 substantially in real time. Note that it is difficult to say that the polishing pad 150 is uniformly worn across the entire surface. In this regard, it is possible to perceive positional dependency of the wear amount of the polishing pad 150 by providing a plurality of indicators 600 as illustrated in FIG. 6.

The alignment mark 300 may also serve as the indicator 600. Conversely, the indicator 600 may also serve as the alignment mark 300. Both the alignment mark 300 and the indicator 600 may be provided respectively. It may be also possible to provide the alignment mark 300 in the lower part of any transparent window 152 and provide the indicator 600 in the lower part of the other transparent window 152.

The substrate polishing apparatus 100 may have an image sensing mechanism 900 in order to observe the transparent window 152 and/or the indicator 600. FIG. 9 is a front cross-sectional view illustrating the substrate polishing apparatus 100 having the image sensing mechanism 900. It is assumed that at least a part of the indicator 600 is located in a place indicated by the arrow extending from the reference numeral “600”. However, since the height (thickness) of the indicator 600 in FIG. 9 is nearly zero, the cross section of the indicator 600 is not illustrated in FIG. 9. Note that this description is not intended to exclude the indicator 600 having a height. For example, in a case where the indicator 600 is formed by any member embedded in the polishing table 110, the indicator 600 may have a height.

The image sensing mechanism 900 is configured to obtain an image and/or video of the indicator 600 through the transparent window 152. That is, the image sensing mechanism 900 observes the indicator 600. In the following description, the “image and/or video” will be simply referred to as an “image”. In addition, in the following description, the “image obtainment” will be simply referred to as “photographing”. In a case where each component is suitably installed, the indicator 600 is placed in the lower part of the transparent window 152. Therefore, the image sensing mechanism 900 can photograph at least a part of the indicator 600 through the transparent window 152. Preferably, the image sensing mechanism 900 is configured to put the entire area of the transparent window 152 into its field of view. Alternatively, the image sensing mechanism 900 may put at least a part of the transparent window 152 into its field of view. In the example of FIG. 9, the image sensing mechanism 900 such as a charge-coupled device (CCD) camera is arranged to face the polishing table 110. An optical element such as a mirror or lens may be disposed in the optical path between the image sensing mechanism 900 and the polishing table 110. The amount of light for the photographing may be insufficient in a case where the polishing table 110 is surrounded by a housing or the like. The substrate polishing apparatus 100 may have a light source for assisting the photographing. A light source 1000 described below may assist the photographing of the image sensing mechanism 900. Preferably, the image sensing mechanism 900 can detect light having the same wavelength as that of the sensing light. The light source for assisting the photographing may irradiate light having the same wavelength as that of the sensing light.

The image sensing mechanism 900 may be controlled by the controller 910. The connection type between the image sensing mechanism 900 and the controller 910 is not limited to wired connection, but they may be connected in a wireless manner (they are connected in a wired manner in the example of FIG. 9). The controller 910 may be provided inside the image sensing mechanism 900 or may be a component separate from the image sensing mechanism 900. The controller 910 may have a storage device 911, a processor 912, and a display 913. The controller 910 may further include other elements. The controller 910 may be connected to any other component of the substrate polishing apparatus 100 as well as the image sensing mechanism 900.

The image sensing mechanism 900 transmits the photographed image to the controller 910. The controller 910 which has obtained the image of the transparent window 152 and/or the indicator 600 from the image sensing mechanism 900 calculates a deterioration level of the transparent window 152 from the images of the transparent window 152 and/or the indicator 600. The controller 910 (more specifically, the processor 912) may determine the deterioration level of the transparent window 152, for example, on the basis of the aforementioned parameters (1) to (5) (such as the brightness of the indicator 600). Alternatively, the deterioration level may be calculated, for example, on the basis of the number or the area of scratches or the like on the transparent window 152.

Specifically, the deterioration level of the transparent window 152 may be calculated using a method including steps of:

photographing the transparent window 152 and/or the indicator 600 using the image sensing mechanism 900;

comparing an image photographed by the image sensing mechanism 900 with an ideal image and/or comparing a characteristic amount calculated from the image photographed by the image sensing mechanism 900 with an ideal characteristic amount; and

calculating a deterioration level of the transparent window 152 on the basis of a comparison result of the step of comparison.

Here, the “ideal image and/or the ideal characteristic amount” refer to “an image and/or a characteristic amount obtained or to be obtained in a case where the transparent window 152 is not deteriorated”.

Before the step of photographing, a step of storing the ideal image and/or the ideal characteristic amount in the storage device 911 may be executed. The ideal image and/or the ideal characteristic amount stored in the storage device 911 may be used in the step of comparison.

The step of comparison may be controlled by the processor 912. In the step of comparison, any image processing technique known in the art may be employed. Here, the “characteristic amount” refers to a parameter (or a parameter value) that can be used in determination of the deterioration level of the transparent window 152. For example, the aforementioned parameters (1) to (5) (such as the brightness of the indicator 600) may be employed as the characteristic amount. Alternatively, the number or the area of scratches on the transparent window 152 may be employed as the characteristic amount. The number of the characteristic amounts used in each step may be one or more. The ideal image and/or the ideal characteristic amount recorded in the storage device 911 may be an image and/or a characteristic amount actually obtained by using a transparent window 152 which is not deteriorated at all. The ideal image and/or the ideal characteristic amount recorded in the storage device 911 may be an image and/or a characteristic amount calculated through simulation or the like.

Before the step of photographing, a step of cleaning a surface of the polishing pad 150 may also be executed. The “cleaning” as used herein refers to cleaning of the surface of the polishing pad 150 in order to remove a foreign object on the transparent window 152. Therefore, the “cleaning” as used herein has a meaning different from that of the terminology “dressing” or the like used in the art. However, if a foreign object on the transparent window 152 can be removed through the dressing, such “dressing” is included in the cleaning. In addition, the “foreign object on the transparent window” as used herein refers to an object that interferes with photographing of the transparent window 152, such as slurry attached to the transparent window 152. If a foreign object is removed through the cleaning, the transparent window 152 and/or the indicator 600 can be suitably photographed. The cleaning may include washing with pure water, gas injection with a blower, or wiping with a wiper. In addition, any other method may also be employed. The step of cleaning may be performed by a user or may be automatically performed under control of the processor 912.

Before the step of photographing, a step of putting at least a part of or a whole area of the transparent window 152 into a field of view of the image sensing mechanism 900 (hereinafter, referred to as “field-of-view adjustment step). The field-of-view adjustment step may be executed by rotating the polishing table 110 and moving the transparent window 152 to a predetermined position. Here, the “predetermined position” refers to a “position where an image can be photographed by the image sensing mechanism 900”. In a case where the image sensing mechanism 900 is configured to be movable, the field-of-view adjustment step may be executed by moving the image sensing mechanism 900. In a case where an optical element is disposed in the optical path between the image sensing mechanism 900 and the transparent window 152, the field-of-view adjustment step may be executed by moving, operating, or adjusting the optical element. In addition, in a case where the polishing head 130 is put into the field of view of the image sensing mechanism 900 during the photographing, a step of moving the polishing head 130 out of the field of view of the image sensing mechanism 900 may also be executed. The movement of each element or the like may be controlled by the processor 912.

Before the step of comparison, a step of calculating a characteristic amount from the image obtained by the image sensing mechanism 900 may be executed. The calculation of the characteristic amount may be controlled by the processor 912. After the step of calculating the deterioration level of the transparent window 152, a step of executing an error processing may be executed if the deterioration level of the transparent window 152 exceeds a predetermined value. The error processing may include a process of displaying a message for urging replacement of the polishing pad 150 on the display 913. The determination on whether or not the deterioration level of the transparent window 152 exceeds a predetermined value may be executed by the processor 912. The display of the message may be controlled by the processor 912. The error processing may include causing the processor 912 to stop the polishing of the substrate 131 using the substrate polishing apparatus 100. In a case where the substrate polishing apparatus 100 has a warning device such as a red lamp or a buzzer, the error processing may include activating the warning device.

After the step of comparison, a step of predicting a remaining service life of the transparent window 152 on the basis of a result of the comparison may also be executed. The prediction of the remaining service life may be executed by the processor 912. Note that the “remaining service life of the transparent window” refers to the polishing time or the number of polishing until the deterioration level of the transparent window exceeds a predetermined value from the start of the prediction step. The remaining service life of the transparent window 152 may also be predicted on the basis of a calculation formula or the like recorded in the storage device 911 in advance. The remaining service life of the transparent window 152 may be predicted by using, as learning data, the images obtained from the image sensing mechanism 900 until the current time and/or the characteristic amount obtained from the image obtained by the image sensing mechanism 900. The learning data may be recorded in the storage device 911. A message indicating the predicted remaining service life may also be displayed on the display 913. If the predicted remaining service life is shorter than a predetermined value, a message warning that expiration of the service life is approaching may be displayed on the display 913. The display of the message may also be controlled by processor 912.

After the deterioration level of the transparent window 152 is calculated, the controller 910 may calculate the wear amount of the polishing pad 150 on the basis of the calculated deterioration level of the transparent window 152.

A result of the calculation of the deterioration level of the transparent window 152 or a result of the prediction of the remaining service life of the transparent window 152 may be compared with the deterioration level or the remaining service life visually observed by a user in practice, and the comparison result may be fed back to the calculation or prediction process. As a result, it is possible to improve accuracy in calculation of the deterioration level or prediction of the remaining service life or compensate for a variation of the prediction.

Although the transparent window 152 having the through-hole 151 is employed in FIG. 9, a transparent window 152 that does not have the through-hole 151 may also be employed (refer to FIGS. 7A and 7B).

In a case where the sensing light passes through the transparent window 152, the deterioration state of the transparent window 152 may be checked without using the indicator 600. FIG. 10 is a front cross-sectional view illustrating the substrate polishing apparatus 100 having the light source 1000. The substrate polishing apparatus 100 of FIG. 10 does not have the indicator 600. Accordingly, the image sensing mechanism 900 of FIG. 10 is configured to photograph at least a part of the transparent window 152 instead of the indicator 600. In FIG. 10, the transparent window 152 of FIG. 7, that is, the transparent window 152 that does not have the through-hole 151 is employed. Accordingly, the configurations of the polishing table 110 and the optical sensor 120 are changed from those of FIG. 9 (refer to the description of FIGS. 7A and 7B). The substrate polishing apparatus 100 of FIG. 10 has the light source 1000. The light source 1000 can irradiate light at least toward the transparent window 152. Specifically, the light source 1000 is configured to irradiate light onto the reflection light optical fiber 123 through the transparent window 152. Preferably, the light source 1000 can irradiate at least light having the same wavelength as that of the sensing light. The light source 1000 may include, for example, a light bulb, a laser device, or the like. An optical element such as a lens or mirror may be disposed in the optical path between the light source 1000 and the transparent window 152.

In the following description, it is assumed that the transmittance of the transparent window 152 is reduced in a case where the transparent window 152 is deteriorated. In addition, for convenient description purposes, in the following description, it is assumed that only the transmittance of the transparent window 152 affects the light amount detected by the optical sensor 120. As the light source 1000 irradiates light onto the transparent window 152, the light arrives at the reflection light optical fiber 123. The light arriving at the reflection light optical fiber 123 is detected by an internal photodetector of the sensor body 121. In a case where the transparent window 152 is not deteriorated at all, the transmittance of the transparent window 152 is maximized. Therefore, in a case where the transparent window 152 is not deteriorated at all, the light amount detected by the optical sensor 120 becomes the maximum value. In a case where the transparent window 152 is deteriorated, and the transmittance of the transparent window 152 is reduced, the light amount detected by the optical sensor 120 also decreases. Therefore, it is possible to calculate the deterioration level of the transparent window 152 by measuring the light amount detected by the optical sensor 120. The deterioration level of the transparent window 152 may be calculated from an absolute value of the light amount detected by the optical sensor 120. The deterioration level of the transparent window 152 may be calculated by comparing the maximum value of the light amount and the light amount of the current time point. The “maximum value of the light amount” refers to a light amount detected when the transparent window 152 is not deteriorated at all, that is, an ideal light amount. If there is another factor that affects the light amount detected by the optical sensor 120, such a factor may also be considered.

Even when the optical property other than the transmittance of the transparent window 152 changes in the case of deterioration of the transparent window 152, it is possible to calculate the deterioration level of the transparent window 152 using a similar method. In a case where the optical property other than the light amount detected by the optical sensor 120 changes as the optical property of the transparent window 152 changes, it is preferable that such a change can be measured by the optical sensor 120. For example, the optical sensor 120 may measure a polarization degree, a wavelength, an incidence angle, or the like of the light in addition to the light amount.

Next, a second method of calculating the deterioration of the transparent window 152 without using the indicator 600 in a case where the sensing light passes through the transparent window 152 will be described. In the method described below, the irradiation light irradiated from the irradiation light optical fiber 122 is employed. In a case where the transparent window 152 is covered by the substrate 131 (refer to the transparent window 152 placed in the left half of FIG. 10), the irradiation light from the irradiation light optical fiber 122 is reflected by the substrate 131. The reflection light is directed to the reflection light optical fiber 123. In this case, the irradiation light and the reflection light (sensing light) pass through the transparent window 152. Therefore, the sensing light is affected by a change of the optical property of the transparent window 152. For example, in a case where the transmittance of the transparent window 152 is reduced by deterioration of the transparent window 152, the transparent window 152 is deteriorated, and the light amount of the reflection light detected by the photodetector of the sensor body 121 is reduced. Therefore, it is possible to calculate the deterioration level of the transparent window 152 by measuring the amount of the sensing light detected by the optical sensor 120. In a case where the optical property other than the light amount detected by the optical sensor 120 changes depending on a change of the optical property of the transparent window 152, it is preferable that the optical sensor 120 can measure such a change. For example, the optical sensor 120 may also measure a polarization degree, a wavelength, an incidence angle, or the like of the light in addition to the light amount. The substrate 131 used to measure the amount of the sensing light may be a substrate 131 that will be polished or is being polished by the substrate polishing apparatus 100. A dummy substrate may also be employed as the substrate 131 in order to reduce influence of the individual differences between the substrates or influence of the polishing progress of the substrate.

Next, a third method of calculating deterioration of the transparent window 152 without using the indicator 600 in a case where the sensing light passes through the transparent window 152 will be described. In the method described below, the irradiation light irradiated from the irradiation light optical fiber 122 is employed. In a case where the transparent window 152 is not covered by the substrate 131, the irradiation light from the irradiation light optical fiber 122 is not blocked by the substrate 131. If the position of the image sensing mechanism 900 is suitable, the irradiation light passes through the transparent window 152 and arrives at the image sensing mechanism 900. The irradiation light is influenced by a change of the optical property of the transparent window 152. For example, in a case where the transmittance of the transparent window 152 is reduced by deterioration of the transparent window 152, the transparent window 152 is deteriorated, and the light amount of the irradiation light detected by the image sensing mechanism 900 is reduced. Therefore, it is possible to calculate the deterioration level of the transparent window 152 by measuring the amount of the irradiation light detected by the image sensing mechanism 900. In a case where the optical property other than the light amount detected by the optical sensor 120 changes as the optical property of the transparent window 152 changes, it is preferable that the image sensing mechanism 900 can measure such a change. For example, the image sensing mechanism 900 may measure a polarization degree, a wavelength, an incidence angle, or the like of the light in addition to the light amount. A change of the optical property of the transparent window 152 may be calculated from the image obtained by the image sensing mechanism 900.

Several embodiments of the present invention have been described hereinbefore. However, the aforementioned embodiments are not to be construed as limiting, but are for descriptive purposes only. Various changes or modifications may be possible without departing from the spirit and scope of the invention, naturally including the equivalents thereof. Furthermore, any combination or omission may be possible for the elements described in claims and specifications as long as at least a part of the aforementioned problems can be addressed, or at least a part of the effects can be achieved.

Note that terminologies used to indicate directions herein are used for convenience purposes. Although the upper, lower, left, and right directions are defined herein on the basis of FIG. 1, the upper direction of FIG. 1 does not necessarily match the vertically upper direction.

This application discloses a substrate polishing apparatus as one embodiment. The substrate polishing apparatus includes: a polishing table for installing a polishing pad having a transparent window; and an indicator provided in the polishing table to check deterioration of the transparent window in a location visually observable through the transparent window.

According to an embodiment of this application, there is provided a substrate polishing apparatus including: a polishing table for installing a polishing pad having a transparent window; and an optical sensor installed in the polishing table to measure a polishing progress of a substrate, wherein the polishing table has an opening for passing an optical fiber extending from the optical sensor, and an indicator for checking deterioration of the transparent window, the indicator is provided on a surface of the polishing table where the polishing pad is installed, and the indicator is provided around the opening.

Using such a substrate polishing apparatus, for example, it is possible to determine the deterioration level of the transparent window by visually observing the indicator. In addition, using such a substrate polishing apparatus, for example, it is possible to determine the wear amount of the polishing pad and the replacement timing of the polishing pad by determining the deterioration level of the transparent window from appearance of the indicator.

According to an embodiment of this application, the substrate polishing apparatus further includes an image sensing mechanism configured to photograph the indicator through the transparent window.

In this substrate polishing apparatus, the image sensing mechanism can photograph the indicator. That is, for example, it is possible to observe the indicator without visual observation of a user.

According to an embodiment of this application, the substrate polishing apparatus further includes a controller configured to calculate a deterioration level of the transparent window from an image obtained by the image sensing mechanism and/or a characteristic amount calculated from the image obtained by the image sensing mechanism.

According to an embodiment of this application, the controller of the substrate polishing apparatus calculates the deterioration level of the transparent window on the basis of a result of comparison between an ideal image and/or an ideal characteristic amount and an image and/or a characteristic amount of the indicator obtained by the image sensing mechanism.

According to these disclosures, it is possible to know details of a process of calculating the deterioration level.

According to an embodiment of this application, the controller of the substrate polishing apparatus executes an error processing when the calculated deterioration level of the transparent window exceeds a predetermined value.

Using such a substrate polishing apparatus, for example, it is possible to stop the use of the deteriorated transparent window.

According to an embodiment of this application, the controller of the substrate polishing apparatus calculates a wear amount of the polishing pad on the basis of the calculated deterioration level of the transparent window.

According to this disclosure, it is possible to calculate the wear amount of the polishing pad from the deterioration level of the transparent window.

According to an embodiment of this application, there is provided a method of calculating a deterioration level of a transparent window provided in a polishing pad installed in a polishing table of a substrate polishing apparatus, the method including: photographing the transparent window and/or an indicator on the polishing table provided in a location visually observable through the transparent window using an image sensing mechanism; comparing between an image photographed by the image sensing mechanism and an ideal image and/or between a characteristic amount calculated from the image photographed by the image sensing mechanism and an ideal characteristic amount; and calculating the deterioration level of the transparent window on the basis of a comparison result obtained in the comparing.

According to an embodiment of this application, there is provided a method of calculating a wear amount of the polishing pad on the basis of the deterioration level of the transparent window calculated in the method described above of calculating the deterioration level of the transparent window.

According to these disclosures, it is possible to know the method of calculating the deterioration level of the transparent window and the method of calculating the wear amount of the polishing pad.

REFERENCE SIGNS LIST

-   -   100 substrate polishing apparatus     -   110 polishing table     -   111 sealing liquid supply path     -   112 sealing liquid discharge path     -   113 sealing liquid source     -   114 rotary joint     -   120 optical sensor     -   121 sensor body     -   122 irradiation light optical fiber     -   123 reflection light optical fiber     -   130 polishing head     -   131 substrate     -   140 polish liquid supply mechanism     -   150 polishing pad     -   151 through-hole     -   152 transparent window     -   300 alignment mark     -   310 first mark     -   320 second mark     -   330 third mark     -   340 fourth mark     -   600 indicator     -   610 opening     -   900 image sensing mechanism     -   910 controller     -   911 storage device     -   912 processor     -   913 display     -   1000 light source 

What is claimed is:
 1. A substrate polishing apparatus comprising: a polishing table for installing a polishing pad having a transparent window; and an indicator provided in the polishing table to check deterioration of the transparent window in a location visually observable through the transparent window.
 2. A substrate polishing apparatus comprising: a polishing table for installing a polishing pad having a transparent window; and an optical sensor installed in the polishing table to measure a polishing progress of a substrate, wherein the polishing table has an opening for passing an optical fiber extending from a main body of the optical sensor and an indicator for checking deterioration of the transparent window, the indicator is provided on a surface of the polishing table where the polishing pad is installed, and the indicator is provided around the opening.
 3. The substrate polishing apparatus according to claim 1, further comprising an image sensing mechanism configured to photograph the indicator through the transparent window.
 4. The substrate polishing apparatus according to claim 3, further comprising a controller configured to calculate a deterioration level of the transparent window from an image obtained by the image sensing mechanism and/or a characteristic amount calculated from the image obtained by the image sensing mechanism.
 5. The substrate polishing apparatus according to claim 4, wherein the controller calculates the deterioration level of the transparent window on the basis of a result of comparison between an ideal image and/or an ideal characteristic amount and an image and/or a characteristic amount of the indicator obtained by the image sensing mechanism.
 6. The substrate polishing apparatus according to claim 4, wherein the controller executes an error processing when the calculated deterioration level of the transparent window exceeds a predetermined value.
 7. The substrate polishing apparatus according to claim 4, wherein the controller calculates a wear amount of the polishing pad on the basis of the calculated deterioration level of the transparent window.
 8. A method for calculating a deterioration level of a transparent window provided in a polishing pad installed in a polishing table of a substrate polishing apparatus, the method comprising: photographing the transparent window and/or an indicator on the polishing table provided in a location visually observable through the transparent window using an image sensing mechanism; comparing between an image photographed by the image sensing mechanism and an ideal image and/or between a characteristic amount calculated from the image photographed by the image sensing mechanism and an ideal characteristic amount; and calculating the deterioration level of the transparent window on the basis of a comparison result obtained in the comparing.
 9. A method for calculating a wear amount of the polishing pad on the basis of the deterioration level of the transparent window calculated in the method according to claim
 8. 